This invention pertains to labeling machines of the kind shown in U.S. Pat. Nos. 2,460,214 and 2,940,630 wherein there are pickers mounted for oscillation between a label magazine and a gripper assembly for transferring labels from the magazine to the gripper assembly which, in turn, transfers the label to a container at a label-applying station. As disclosed in the aforesaid patents each picker comprises two elongate blades arranged edge to edge with their surfaces in a common plane. Adhesive is applied to the surfaces of the picker blades by a transfer roll which, in turn, receives adhesive from a pick-up roll mounted in a container, just before the picker is moved into engagement with the label supported by the magazine, to pick the label from the magazine and following picking the picker moves to a transfer position for transferring the label to the gripper assembly. At the latter position the gripper assembly, which is provided with vacuum means, takes hold of the adhesive-coated label whereupon the picker blades are moved apart far enough to permit the gripper assembly to move forwardly between the blades toward the container to carry the label into engagement with the container. The lateral movement of the blades at the place of transfer, in conjunction with the pressure between the gripper assembly and the blades of the picker at the place of transfer, helps to spread the adhesive uniformly over the face of the label. In the aforesaid machines the pick-up roll is provided with a uniform thickness of adhesive by means of a doctor blade and this is applied to the transfer roll by holding the latter in contact with the pick-up roll until the transfer roll has made at least one complete rotation. In these machines the pick-up roll is driven but the transfer roll is not; however, the adhesive used is sufficiently tacky so that contact of the transfer roll with the pick-up roll insures rotation of the transfer roll. Hence all that is required to insure application of a fresh coating of adhesive to the entire surface of the transfer roll is to hold the transfer roll in engagement with the pick-up roll until it has made one complete revolution. There are certain types of plastic containers to which labels are applied that require the use of adhesive which is almost like water and which lacks the tackiness of the gelly-like animal glue heretofore used. When such a watery adhesive is employed it often has so little tackiness that the undriven transfer roll will not be rotated while in engagement with the pick-up roll and merely skids relative to the surface thereof even though antifriction bearings are employed. Consequently, there will be no adhesive on the surface of the transfer roll when the latter is moved along the surface of the picker for application to the picker. Additionally, because of the lack of tackiness the transfer roll may also skid along the surface of the picker, that is, as it is moved therealong so that even if there is some adhesive on the surface of the transfer roll it will not be transferred uniformly to the surface of the picker. To insure complete coating of the transfer roll with such a watery adhesive and to insure uniform transfer to the picker, the transfer roll must be driven while engaged with the pick-up roll and while in engagement with the picker.
If the length of the picker corresponds exactly to the circumferential length of the transfer roll, one complete revolution of the transfer roll will insure a fresh coating of adhesive to the entire surface of the picker. However, to avoid building machines with a picker and transfer roll having a 1:1 relation for each label size, it is customary to provide machines with pickers suitable for applying labels of all sizes and so that not only one label may be applied but several labels may be applied at the same time, for example, to the body, shoulder and neck. To do this it is necessary to make the picker of sufficient length to accommodate not only labels of all sizes but several labels at a time and so it is customary to provide the machine with pickers of sufficient length to receive all of the labels to be applied. the pickers are made in lengths of 12, 81/2 and 51/2 inches, -- this range being such as to take care of the complete range of sizes of containers ordinarily encountered. The transfer roll for a 12 inch picker is 2 inches in diameter and so its circumference is approximately 6.2 inches long. It is obvious therefore that even if a uniform coating of adhesive is applied to the surface of the transfer roll by positively rotating it while in engagement with the pick-up roll the major portion of the adhesive will be applied to the upper portion of the picker surface, that is to the first 6.2 inches during the first complete turn thereof and that the remainder of the surface may not receive enough adhesive to provide for a proper bond. When employing conventional adhesive this condition was not too serious because some adhesive tended to stay with the surface of the transfer roll and to be spread on the remaining surface by the second rotation of the transfer roll. However, a watery adhesive does not exhibit these characteristics with the result that the portion of the picker surface beyond that corresponding to the circumferential length of the transfer roll receives substantially no adhesive. It might be thought that the doctor could be set to provide a thicker coating of adhesive on the transfer roll; however, it has been found that the transfer roll will not accumulate an excess of adhesive in a sufficient amount to provide for applying a second coating of adhesive to the picker beyond the first complete turn of the transfer roll in engagement with the picker. To achieve a uniform coating of the entire surface of the picker the transfer roll must be driven while in engagement with the picker so as to make only one complete turn while travelling from one end of the picker surface to the other.